System and method of magnetic shielding for sensors

ABSTRACT

A system includes a magnetostrictive sensor. The magnetostrictive sensor includes a driving coil configured to receive a first driving current and to emit a first magnetic flux portion through a target and a second magnetic flux portion. The magnetostrictive sensor also includes a first sensing coil configured to receive the first magnetic flux portion and to transmit a signal based at least in part on the received first magnetic flux portion. The received first magnetic flux portion is based at least in part on a force on the target. The magnetostrictive sensor further includes a magnetic shield disposed between the driving coil and the first sensing coil. The magnetic shield is configured to reduce the second magnetic flux portion received by the first sensing coil.

BACKGROUND

The subject matter disclosed herein relates generally to sensors, andmore particularly to magnetic shields for magnetostrictive sensors.

Sensors are used in a variety of industries to sense vibration, torque,speed, force, position, and other parameters. In certain applications,the performance of the sensor may decrease due to electrical and/ormagnetic interference. Furthermore, some sensors may depend on magneticprinciples for their operation, and thus a leakage magnetic flux mayresult in performance degradation.

BRIEF DESCRIPTION

Certain embodiments commensurate in scope with the present disclosureare summarized below. These embodiments are not intended to limit thescope of the claims, but rather these embodiments are intended only toprovide a brief summary of certain embodiments. Indeed, embodiments ofthe present disclosure may encompass a variety of forms that may besimilar to or different from the embodiments set forth below.

In a first embodiment, a system includes a magnetostrictive sensor. Themagnetostrictive sensor includes a driving coil configured to receive afirst driving current and to emit a first magnetic flux portion througha target and a second magnetic flux portion. The magnetostrictive sensoralso includes a first sensing coil configured to receive the firstmagnetic flux portion and to transmit a signal based at least in part onthe received first magnetic flux portion. The received first magneticflux portion is based at least in part on a force on the target. Themagnetostrictive sensor further includes a magnetic shield disposedbetween the driving coil and the first sensing coil. The magnetic shieldis configured to reduce the second magnetic flux portion received by thefirst sensing coil.

In a second embodiment, a system includes a magnetostrictive sensor. Themagnetostrictive sensor includes a driving coil configured to receive afirst driving current and to emit a first magnetic flux portion througha target and a second magnetic flux portion. The magnetostrictive sensoralso includes a first sensing coil configured to receive the firstmagnetic flux portion and to transmit a signal to a controller based atleast in part on the received first magnetic flux portion. Themagnetostrictive sensor further includes a magnetic shield comprising aflexible circuit. The magnetic shield is disposed between the drivingcoil and the first sensing coil and the magnetic shield is configured toreduce the second magnetic flux portion received by the first sensingcoil. The system also includes the controller configured to determine aforce applied to the target based at least in part on the signal.

In a third embodiment, a method includes supplying a first current to adriving coil of a magnetostrictive sensor. The method also includesemitting a first magnetic flux portion from the driving coil through atarget. Furthermore, the method includes emitting a second magnetic fluxportion from the driving coil. Moreover, the method includes sensing thefirst magnetic flux portion with a sensing coil of the magnetostrictivesensor. Still, the method includes reducing the second magnetic fluxportion received by the sensing coil based at least in part on amagnetic shield of the magnetostrictive sensor disposed between thedriving coil and the sensing coil.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will be better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a side view of an embodiment of a magnetostrictive sensingsystem with a magnetic shield in accordance with the present disclosure;

FIG. 2 is a side view of an embodiment of a magnetostrictive sensingsystem with a magnetic shield in accordance with the present disclosure;

FIG. 3 is a perspective view of an embodiment of a magnetic shield inaccordance with the present disclosure;

FIG. 4 is a perspective view of an embodiment of a magnetic shield inaccordance with the present disclosure;

FIG. 5 is a perspective view of an embodiment of a magnetic shield inaccordance with the present disclosure;

FIG. 6 is a top view of the external side of the magnetic shield in FIG.5;

FIG. 7 is a top view of the internal side of the magnetic shield in FIG.5;

FIG. 8 is a side view of an embodiment of a magnetostrictive sensingsystem with a magnetic shield in accordance with the present disclosure;

FIG. 9 is a top view of a magnetostrictive sensing system having anouter magnetic shield;

FIG. 10 is a perspective view of an embodiment of the sensor head of themagnetostrictive sensing system as illustrated in FIG. 1; and

FIG. 11 is a top view of the embodiment of the sensor head in FIG. 10.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

Ferromagnetic materials have a magnetostrictive property that causes thematerials to change shape in the presence of an applied magnetic field.Conversely, when a force is applied to a ferromagnetic material to causethe shape to change, the magnetic properties (e.g., magneticpermeability) of the material also change. Therefore, ferromagneticmaterials can convert magnetic energy into potential energy, orpotential energy into magnetic energy. Accordingly, ferromagneticmaterials may be used for sensors such as force sensors, positionsensors, and torque sensors. A magnetostrictive sensor may generate amagnetic flux to pass through a ferromagnetic material.

A magnetostrictive sensor may include a driving coil to generatemagnetic flux and a sensing pole to sense the magnetic flux passingthrough a ferromagnetic material (e.g., a target material). Because thechanges in the measured magnetic flux depend partly on the changes inmagnetic permeability of the ferromagnetic material, which in turn arerelated to the amount of force applied to the ferromagnetic material,measurement of the magnetic flux may be used to sense and/or calculatethe value of the applied force. Unfortunately, a leakage magnetic fluxfrom the driving coil to the sensing coil may occur in themagnetostrictive sensor. The leakage magnetic flux does not pass throughthe ferromagnetic material and, therefore, provides little informationon the magnetic permeability of the ferromagnetic material. In addition,because the leakage magnetic flux also passes through the sensing coil,the leakage magnetic flux may be a noise relative to the measuredmagnetic flux that is from the driving coil to the sensing coil passingthrough the ferromagnetic material. Such noise may reduce the dynamicrange of the magnetostrictive sensor.

The present disclosure provides a magnetostrictive sensor with amagnetic shield. As discussed in greater detail below, the magneticshield may be disposed in the space between a driving pole and a sensingpole of the magnetostrictive sensor. The magnetic shield may also bedisposed about the driving pole. The magnetic shield may reduce oreliminate the leakage flux between the driving pole and the sensingpole. Advantageously, the resulting magnetostrictive sensor may have anincreased dynamic sensing range. In addition, the magnetic shield mayimprove the signal to noise ratio of the magnetostrictive sensor.Furthermore, by including the magnetic shield, the magnetostrictivesensor may use a simpler conditioning circuitry.

FIG. 1 is a side view of an embodiment of a magnetostrictive sensingsystem 10 with a magnetic shield 11 (e.g., a magnetic shield 12) inaccordance with the present disclosure. The magnetostrictive sensingsystem 10 may be used for sensing a force applied to a target material14 of a machine or equipment 15, such as a turbomachine (e.g., a turbineengine, a compressor, a pump, or a combination thereof), a generator, acombustion engine, or a combination thereof. The target material 14 maybe a ferromagnetic material including, but not limited to, iron, steel,nickel, cobalt, alloys of one or more of these materials, or anycombination thereof. The magnetostrictive sensing system 10 includes asensor head 16 positioned proximate to the target material 14, therebyforming a gap 17 between the sensor head 16 and the target material 14.The sensor head 16 may be coupled to a frame or fixture to maintain thesensor head 16 in the proper orientation and/or position.

The sensor head 16 has a core 18 that may be formed from a ferromagneticmaterial. The core 18 has at least two ends, such as a driving pole 20and a sensing pole 22. A driving coil 24 and a sensing coil 26 aredisposed about (e.g., wrapped around) the driving pole 20 and thesensing pole 22, respectively. A power source 28 (e.g., electricaloutlet, electrical generator, battery, etc.) provides an AC current(e.g., first driving current) to the driving coil 24. The first drivingcurrent passes through the driving coil 24 to induce a magnetic flux 30that emanates from the driving coil 24. A controller 32 electronicallycoupled to the power source 28 is configured to control characteristicsof the first driving current delivered to the driving coil 24 by thepower source 28. For example, the controller 32 may control thefrequency, amplitude, or the like, of the first driving current. Thecontroller 32 may be coupled to the power source 28 by wired or wirelessconnections. Wireless communication devices such as radio transmittersmay be integrated with the controller 32 to transmit the signals to areceiver integrated with the power source 28.

The controller 32 may include a distributed control system (DCS) or anycomputer-based workstation that is fully or partially automated. Forexample, the controller 32 may be any device employing a general purposeor an application-specific processor 34, both of which may generallyinclude memory circuitry 36 for storing instructions related tofrequencies, amplitudes of currents, for example. The processor 34 mayinclude one or more processing devices, and the memory circuitry 36 mayinclude one or more tangible, non-transitory, machine-readable mediacollectively storing instructions executable by the processor 34 toperform the methods and control actions described herein.

Such machine-readable media can be any available media other thansignals that can be accessed by the processor or by any general purposeor special purpose computer or other machine with a processor. By way ofexample, such machine-readable media can include RAM, ROM, EPROM,EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium which can be used tocarry or store desired program code in the form of machine-executableinstructions or data structures and which can be accessed by theprocessor or by any general purpose or special purpose computer or othermachine with a processor. When information is transferred or providedover a network or another communications connection (either hardwired,wireless, or a combination of hardwired or wireless) to a machine, themachine properly views the connection as a machine-readable medium.Thus, any such connection is properly termed a machine-readable medium.Combinations of the above are also included within the scope ofmachine-readable media. Machine-executable instructions includes, forexample, instructions and data which cause the processor or any generalpurpose computer, special purpose computer, or special purposeprocessing machine to perform a certain function or group of functions.

As illustrated, a first magnetic flux portion 38 permeates the targetmaterial 14, passes through the sensing coil 26, and returns to thedriving coil 24 via the core 18. The sensing coil 26 may be used tomeasure the first magnetic flux portion 38. A force (e.g., compressive,tensile, torsional, etc.) applied to the target material 14 may changethe permeability of the target material 14, thereby causing the firstmagnetic flux portion 38 to change. The sensing coil 26 is configured totransmit a signal indicative of the changes in the first magnetic fluxportion 38 to the controller 32. The processor 34 of the controller 32may process the signal received from the sensing coil 26 to calculatethe force applied to the target material 14. For example, the processor34 may execute pre-stored and/or user-defined algorithms in the memory36 to calculate the magnitude and/or direction of the force applied tothe target material 14 based on the characteristics of the targetmaterial 14, the sensor head 16, and the first driving current. Thesignal from the sensing coil 26 may be communicated by wired or wirelessconnections to the controller 32. In some embodiments, wirelesscommunication devices, such as radio transmitters, may be integratedwith the sensor head 16 (e.g., proximate to the sensing coil 26) totransmit the signals to a receiver integrated with the controller 32.The signal received from the sensing coil 26 may also be processed withother electronic components, such as an amplifier, a filter, or thelike, before or after being processing by the processor 34 of thecontroller 32.

A second magnetic flux portion 40 emitted by the driving coil 24 mayenter the sensing coil 26 without permeating the target material 14, asillustrated in FIG. 1. The second magnetic flux portion 40 may also bereferred to as the leakage magnetic flux 40. As noted above, the leakagemagnetic flux 40 provides little information on the magneticcharacteristics (e.g., magnetic permeability) of the target material 14because the leakage magnetic flux 40 does not permeate the targetmaterial 14. Accordingly, the leakage magnetic flux 40 may be anundesirable noise signal sensed by the sensing coil 26 relative to thesignal from the first magnetic flux portion 38. The noise from theleakage magnetic flux 40 may be significant compared to the measuredfirst magnetic flux portion 38. As discussed below, the magnetic shield12 may help to reduce or eliminate noise associated with the leakagemagnetic flux 40 by substantially or entirely blocking the leakagemagnetic flux 40. Accordingly, the magnetic shield 12 may improveaccuracy of sensor measurements, and thus enable better control of themachine or equipment, such as a turbomachine (e.g., a turbine engine, acompressor, a pump, or a combination thereof), a generator, a combustionengine, or a combination thereof.

In operation, the controller 32 may send a control signal to the powersource 28 to deliver a desired AC current to the driving coil 24. Thedriving coil 24 emits the first magnetic flux portion 38 that permeatesthe target material 14 and is detected by the sensing coil 26. A changein the first magnetic flux portion 38 emitted from the driving coil 24to the first magnetic flux portion 38 sensed by the sensing coil 26 dueto a force applied to the target material 14 may be measured by themagnetostrictive sensing system 10. A signal corresponding to suchchange may be transmitted to the controller 32. The processor 34 of thecontroller 32 may process the signal received from the sensing coil 26to obtain a measurement of the force applied to the target material 14.In addition, the driving coil 24 may also emit the second (i.e.,leakage) magnetic flux portion 40 that does not permeate the targetmaterial 14. The corresponding signal from the leakage magnetic flux 40sensed by the sensing coil 26 may constitute noise relative to themeasured signal from the first magnetic flux portion 38.

In order to reduce or eliminate the sensed leakage flux 40 present inthe magnetostrictive sensing system 10, the magnetic shield 12 inaccordance with the present disclosure may be disposed between thedriving pole and the sensing pole. As illustrated, the magnetic shield12 is disposed in the space 42 between the driving pole 20 and thesensing pole 22. As discussed in greater detail below, the magneticshield 12 may be a split tube or annulus formed from a material with ahigh magnetic permeability. Additionally, or in the alternative, themagnetic shield 12 may be a flexible printed circuit board rolled up toa tube or annulus. Additionally, or in the alternative, the magneticshield 12 may be a flexible printed circuit board rolled up to a tube orannulus that is provided with an additional driving current to emit acounter-active magnetic flux to the leakage magnetic flux 40, therebyproviding active magnetic shielding. As illustrated, the leakagemagnetic flux 40 sensed by the sensing coil 26 may be reduced oreliminated by the magnetic shield 12 (e.g., an active and/or passivemagnetic shield). Accordingly, the leakage magnetic flux 40 isillustrated with a dashed line.

The driving coil 24 has a length 44 along an axis 46 substantiallyperpendicular to the portion in the core 18 connecting the driving pole20 and the sensing pole 22, and the sensing coil 26 has a length 48along the axis 46. The magnetic shield 12 has a length 50 along an axis47 parallel to the axis 46. A longer length of the magnetic shield 12may have less sensed leakage flux than a shorter length of the magneticshield 12, the length 50 of the magnetic shield 12 is substantially thesame or greater than the length 44 of the driving coil 24 and the length48 of the sensing coil 26. Accordingly, the magnetic shield 12 may bedisposed between the driving pole 20 and the sensing pole 22 such thatthe magnetic shield 12 substantially covers the full length of thedriving coil 24 and/or the full length of the sensing coil 26.

In some embodiments in accordance with the present disclosure, themagnetostrictive sensing system 10 may include more than one magneticshield 12. For example, more than one magnetic shield 12, coupled witheach other in any suitable manner (e.g., in series, in parallel,concentric, coaxial, telescopic, or any combination thereof), may bedisposed in the space 42 between the driving pole 20 and the sensingpole 22.

FIG. 2 illustrates an embodiment of a magnetostrictive sensing system 60that includes a magnetic shield 11 (e.g., a magnetic shield 62) disposedabout (e.g., wrapped around) the driving coil 24 of the driving pole 20.Additionally, or in the alternative, the magnetic shield 62 may bedisposed about (e.g., wrapped around) the sensing coil 26 of the sensingpole 22. As discussed in greater detail below, the magnetic shield 62may be a split tube or annulus formed from a material with a highmagnetic permeability. Additionally, or in the alternative, the magneticshield 62 may be a flexible printed circuit board rolled up to a tube orannulus. As illustrated, the leakage magnetic flux 40 sensed by thesensing coil 26 may be reduced or eliminated by the magnetic shield 62.Accordingly, the leakage magnetic flux 40 is illustrated with a dashedline.

The magnetic shield 62 has a length 64 along the axis 46. Similar to theembodiment discussed above with reference to FIG. 1, a longer length ofthe magnetic shield 62 may have less sensed leakage flux than a shorterlength of the magnetic shield 62. Accordingly, the length 64 of themagnetic shield 62 is substantially the same or greater than the length44 of the driving coil 24 and the length 48 of the sensing coil 26. Themagnetic shield 62 may be disposed about the driving pole 20 such thatthe magnetic shield 62 substantially covers the full length of thedriving coil 24. Additionally, or in the alternative, the magneticshield 62 may be disposed about the sensing pole 22 such that themagnetic shield 62 substantially covers the full length of the sensingcoil 26.

In some embodiments in accordance with the present disclosure, more thanone magnetic shield 62, coupled with each other in any suitable manner(e.g., in series, in parallel, concentric, coaxial, telescopic, or anycombination thereof), may be disposed about (e.g., wrapped around) thedriving coil 24 of the driving pole 20. In some embodiments, one or moremagnetic shields 62 may be disposed about the driving coil 24 of thedriving pole 20 together with one or more magnetic shields 12 (asillustrated in FIG. 1) disposed in the space 42 between the driving pole20 and the sensing pole 22.

FIG. 3 illustrates an embodiment of a magnetic shield 11 (e.g., amagnetic shield 70) in accordance with the present disclosure, which maybe disposed in the space 42 between the driving pole 20 and the sensingpole 22 (e.g., as shown in FIG. 1), or disposed about (e.g., wrappedaround) the driving coil 24 of the driving pole 20 (e.g., as shown inFIG. 2), or a combination thereof. An axial axis 72, a radial axis 74,and a circumferential axis 76 are utilized herein to describe themagnetic shield 70. As illustrated, the magnetic shield 70 is a splitcylindrical tube. The magnetic shield 70 has a length 78 along the axialaxis 72. The length 78 of the magnetic shield 70 may be substantiallythe same or greater than the length of the driving coil 24 and thesensing coil 26 in a magnetostrictive sensing system 10 (e.g., thelength 44 of the driving coil 24 and the length 48 of the sensing coil26 in FIGS. 1 and 2).

The magnetic shield 70 includes a shell 80 (e.g., outer annular wall)that has a split 82 (e.g., an axial opening) along the axial axis 72.The split 82 of the magnetic shield 70 is for breaking the inducedcurrent path around the circumferential axis 76. The shell 80encompasses a space 84 such that the driving pole 20 with the drivingcoil 24 may be fit into the space 84 without contacting the inside wall86 of the shell 80. The split 82 may have any suitable size 88 along thecircumferential axis 76, for example, less than half (e.g.,approximately 3, 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 135, 175degrees) of the circumference of the shell 80 along the circumferentialaxis 76. The shell 80 may also have any suitable thickness 90,including, but not limited to, between approximately 50 μm and 1000 μm,between approximately 100 μm and 750 μm, between approximately 150 μmand 500 μm, between approximately 200 μm and 400 μm, or betweenapproximately 250 μm and 300 μm. The magnetic shield 70 may be orientedin the space 42 such that the split 82 is not disposed directly betweenthe driving coil 24 and the sensing coil 26.

The magnetic shield 70 may be fabricated from a material with a highmagnetic permeability, such as a material with a relative permeabilitybetween approximately 100 and 100,000, such as between approximately 200and 90,000, between approximately 300 and 70,000, between approximately500 and 50,000, between approximately 1,000 and 30,000, betweenapproximately 2,000 and 20,000, or between approximately 5,000 and10,000. The high magnetic permeability material of the magnetic shield70 may include iron, Mu-metal, cobalt-iron, permalloy, nanoperm,electrical steel, ferrite, carbon steel, nickel, or any combinationthereof. In some embodiments, the magnetic shield 70 may be manufacturedby any suitable methods (e.g., casting, machining, molding, manual, orany combination thereof) to roll up a sheet of high magneticpermeability material as discussed herein to the desirable shape (e.g.,with a cross section of a split circle, square, rectangle, triangle, oroval).

As illustrated in FIG. 3, the magnetic shield 70 is substantially acylindrical tube. In some embodiments, the magnetic shield 70 may haveany suitable shape. For example, the cross section of magnetic shield 70on the plane defined by the axes 74 and 76 may be substantially asquare, a rectangle, a triangle, or an oval. In some embodiments, themagnetic shield 70 may also include a tapered portion at one or both ofthe two axial ends of the magnetic shield 70.

FIG. 4 illustrates an embodiment of a magnetic shield 11 (e.g., amagnetic shield 92) with tapered portions 93, 94 at both axial ends.Each of the tapered portions 93, 94 is angled inward (e.g., toward thespace 84) with an angle 95 with respect to the axial axis 72. The angle95 may be between approximately 1 degree and 90 degrees, such as betweenapproximately 5 degrees and 80 degrees, between approximately 10 degreesand 75 degrees, between approximately 15 degrees and 70 degrees, betweenapproximately 20 degrees and 65 degrees, between approximately 30degrees and 60 degrees, or between approximately 40 degrees and 50degrees.

Each of the tapered portions 93, 94 has a length 96 along the axial axis72. The length 96 may be any suitable length such that the driving pole20 with the driving coil 24 may be fit into the space 84 withoutcontacting an edge 97 of each of the tapered portions 93, 94. Althoughthe illustrated tapered portions 93, 94 have the same dimensions (e.g.,the length 96 along the axial axis 72, and the angle 95 with respect tothe axial axis 72), in some embodiments the tapered portions 93, 94 mayhave different dimensions.

FIGS. 5, 6, and 7 are diagrams of an embodiment of a magnetic shield 11(e.g., a magnetic shield 100) that may be disposed in the space 42between the driving pole 20 and the sensing pole 22 (e.g., as shown inFIG. 1), or disposed about (e.g., wrapped around) the driving coil 24 ofthe driving pole 20 (e.g., as shown in FIG. 2), or a combinationthereof. Similar to the magnetic shield 70, the magnetic shield 100, asillustrated in FIG. 5, is substantially a cylindrical tube. In someembodiments, the magnetic shield 100 may have any suitable shape. Forexample, the cross section of the magnetic shield 100 may besubstantially a square, a rectangle, a triangle, or an oval.

As illustrated in FIGS. 6 and 7, the magnetic shield 100 is asubstantially rectangular flexible printed circuit board 102 rolled upto a substantially cylindrical tube. The magnetic shield 100 has anexternal side 104 and an internal side 106, which are illustrated inFIGS. 6 and 7, respectively. These two sides of the magnetic shield 100may also be referred to herein as the front side 104 and the back side106 of the printed circuit board 102.

FIG. 6 illustrates an embodiment of the front side 104 of the printedcircuit board 102. As illustrated, the front side 104 of the printedcircuit board 102 may include a substrate layer 108 and a printedpattern 110. The substrate layer 108 may be fabricated from a flexiblematerial such as FR4 (e.g., a composite material composed of wovenfiberglass cloth with an epoxy resin binder that is flame resistant),kapton, or polyamide, or any combination thereof. The substrate layer108 may have a thickness between approximately 200 μm to 5 mm, 300 μm to4 mm, 500 μm to 2 mm, 800 μm to 1.5 mm, or 1 mm to 1.2 mm.

The printed pattern 110 is printed or otherwise disposed onto thesubstrate layer 108. The printed pattern 110 may be a spiral coil aroundthe printed circuit board 102. In some embodiments, the printed pattern110 may be connected lines substantially parallel to either side 104,106 of the printed circuit board 102. The printed pattern 110 maysubstantially cover the front side 104 of the printed circuit board 102.In other embodiments, the printed pattern 110 may substantially coverboth the front side 104 and the back side 106, for example, with thespiral coils on both sides 104, 106 around a same direction (e.g.,counterclockwise or clockwise). A first end 112 of the printed pattern110 is on the front side 104 of the printed circuit board 102, and asecond end 116 of the printed pattern 110 is on the back side 106 of theprinted circuit board 102 through a hole (e.g., via) 118 on thesubstrate layer 108 of the printed circuit board 102. The first end 112of the printed pattern 110 may be coupled to a resistor 114. Theresistor is configured to properly dissipate the electrical energygenerated from the leakage flux such it may have minimum backelectromotive force to the driving coil 24. An end 117 of the resistor114 is electrically connected to the second end 116 of the printedpattern 110 through a hole (e.g., via) 119 on the substrate layer 108 ofthe printed circuit board 102.

The printed pattern 110 may have a thickness (e.g., height arising ontop of the substrate layer 108) of between approximately 10 μm to 1 mm,20 μm to 800 μm, 30 μm to 500 μm, 40 μm to 300 μm, 50 μm to 200 μm, or70 μm to 100 μm. The printed pattern 110 may be fabricated from amaterial with a high electrical conductivity, such as copper, silver,gold, aluminum, calcium, tungsten, zinc, nickel, lithium, iron, tin,platinum, carbon steel, or any combination thereof.

The magnetic shield 100 may be rolled or formed to the desirable shape(e.g., a cylindrical tube) with no split between two ends 122, 124 ofthe printed circuit board 102. For example, the overlapping ends 122,124 may form an overlapping region 120 when the printed circuit board102 is rolled up to form the cylindrical shape. The purpose ofoverlapping region is to ensure a complete coverage of the leakage fluxin radial directions. As discussed above, the magnetic shield 100 mayreduce or eliminate the leakage magnetic flux 40 between the drivingcoil 24 and the sensing coil 26 of the magnetostrictive sensing system10.

FIG. 8 illustrates an embodiment of a magnetic shield 11 (e.g., anactive magnetic shield 130) in accordance with the present disclosure.The magnetic shield 130 may be disposed in the space 42 between thedriving pole 20 and the sensing pole 22 of a magnetostrictive sensingsystem 132 (e.g., as shown in FIG. 1). The magnetic shield 130 may begenerally the same as the magnetic shield 100 in a generally flatfashion as illustrated in FIGS. 6, and 7 (e.g., without being rolled upto a substantially cylindrical tube). The front side 104 of the magneticshield 130 may generally face either the driving pole 20 or the sensingpole 22. In some embodiments, the magnetic shield 130 may exclude theresistor 114. The magnetic shield 130 is provided with an AC current toemit additional magnetic flux, as described in greater detail below.Accordingly, the magnetic shield 130 may be referred to as an activemagnetic shield. In contrast, the magnetic shield 100 is not providedwith any current, thereby no additional magnetic flux is emitted by themagnetic shield 100. Accordingly, the magnetic shield 100 may bereferred to as a passive magnetic shield.

The two ends 112, 116 of the printed pattern 110 in the magnetic shield130 are not connected with one another via the hole 119 but areelectrically coupled to a power source 134. The power source 134 may bethe same or separate from the power source 28. The power source 134provides an AC current (e.g., a second driving current) to the printedpattern 110 of the active magnetic shield 130. The second drivingcurrent through the printed pattern 110 induces a third magnetic fluxportion 136 and a fourth magnetic flux portion 138. As noted above, thecontroller 32 is electronically coupled to the power source 134. Thecontroller 32 is configured to control characteristics (e.g., frequency,amplitude) of the second driving current delivered to the printedpattern 110 by the power source 28. In some embodiments, a combinedpower source (e.g., combining the power sources 28 and 134) may be usedto provide power to the driving coil 24 and the magnetic shield 130.

As illustrated, the third magnetic flux portion 136 permeates the targetmaterial 14. The fourth magnetic flux portion 138 passes through thedriving coil 24, the sensing coil 26, and the core 18 without permeatingthe target material 14, similar to the leakage magnetic flux 40. Inaccordance with the present disclosure, the second driving current hasthe same frequency as, but the opposite phase to, the first drivingcurrent. Accordingly, the fourth magnetic flux portion 138 has anopposite direction of the leakage magnetic flux 40 at a given timeduring operation. The magnitude of the fourth magnetic flux portion 138may be tuned to be substantially the same as the magnitude of theleakage magnetic flux 40. Through tuning the fourth magnetic fluxportion 138, the overall leakage magnetic flux (e.g., sum of the fourthmagnetic flux portion 138 and the leakage magnetic flux 40) between thedriving coil 24 and the sensing coil 26 may be reduced or eliminated.Because the active magnetic shield 130 is provided with a drivingcurrent (e.g., the second drive current) to actively emit a magneticflux (e.g., the fourth magnetic flux portion 138) to negativelycounteract the leakage magnetic flux 40, the printed pattern 110 of themagnetic shield 130 may also be referred to herein as a compensationcoil 110.

As noted above, the magnitude of the fourth magnetic flux portion 138may be tuned to be substantially the same as the magnitude of theleakage magnetic flux 40. The magnitude of the fourth magnetic fluxportion 138 depends, at least, on magnitude of the second drivingcurrent and the number of turns of the printed pattern 110. Accordingly,by tuning the magnitude of the second driving current and/or the numberof turns of the printed pattern 110, the magnitude of the fourthmagnetic flux portion 138 may be tuned. In some embodiments, the numberof turns of the printed pattern 110 of the magnetic shield 130 is thesame as the number of coils of the driving coil 24. When in operation,the controller 32 may send a control signal to the power source 28 todeliver two driving currents to the driving coil 24 and the magneticshield 130, respectively, where the two driving currents havesubstantially the same magnitude but the opposite phase. Accordingly,the leakage magnetic flux 40 due to the first driving current may besubstantially reduced or eliminated by the fourth (or compensation)magnetic flux portion 138 with substantially the same magnitude but theopposition direction due to the second driving current.

Regardless of the disposition of the magnetic shield 11 (e.g., as shownin FIGS. 1 and 2), the number of the magnetic shield 11 (e.g., one ormore), or the configurations and/or shapes of the magnetic shield (e.g.,the magnetic shields 70, 92, 100, 130), the magnetostrictive sensingsystems 10, 60, 132 may additionally include an outer magnetic shieldenclosing the sensor head 16. The outer magnetic shield may reduceexternal electromagnetic interference received by the driving coil andthe sensing coil. FIG. 9 illustrates a top view of an embodiment of amagnetostrictive sensing system 140 incorporating such an outer magneticshield 142. As discussed above, the magnetostrictive sensing system 140includes the sensor head 16. The sensor head 16 includes the core 18,the driving pole 20, and the sensing pole 22. The driving coil 24 isdisposed about the driving pole 20, and the sensing coil 26 is disposedabout the sensing pole 22. As illustrated, the magnetostrictive sensingsystem 140 also includes a magnetic shield 11 (e.g., a magnetic shield144) in accordance with the present disclosure (e.g., the magneticshields 70, 92, 100). While the magnetic shield 144 illustrated in FIG.9 is disposed about the driving pole 20, the magnetic shield 144, asnoted above, may be in any configuration, or disposed in any spacebetween the driving pole 20 and the sensing pole 22. For example, themagnetic shield 144 may be disposed in the space 42.

As illustrated, the magnetostrictive sensing system 140 also includesthe outer magnetic shield 142. The outer magnetic shield 142 may includeone or more layers for reducing the magnetic interference from anoutside source. For example, in some embodiments, the outer magneticshield 142 may include, but is not limited to, one or more layers ofmaterial with a high conductivity to reduce high frequency interference.Such high electrical conductivity material may include copper, silver,gold, aluminum, calcium, tungsten, zinc, nickel, lithium, iron, tin,platinum, carbon steel, or any combination thereof.

Alternatively or additionally, the outer magnetic shield 142 may includeone or more layers of material with a high magnetic permeability toreduce low frequency interference. Such material has a relativepermeability between approximately 100 to 100,000, 200 to 90,000, 300 to70,000, 500 to 50,000, 1,000 to 30,000, 2,000 to 20,000, or 5,000 to10,000. Such high magnetic permeability material may include, but is notlimited to, iron, Mu-metal, cobalt-iron, permalloy, nanoperm, electricalsteel, ferrite, carbon steel, nickel, or any combination thereof.

As illustrated in FIG. 1, the sensor head 16 includes a driving pole 20and at least one sensing pole 22 with the corresponding driving coil 24and at least one sensing coil 26 disposed thereabout, respectively. Someembodiments of the sensor head 16 may include one or more driving polesand one or more sensing poles. FIG. 10 is a perspective view of anembodiment of a sensor head 150 with one driving pole 152 and foursensing poles 154, 156, 158, 160. FIG. 11 is a top view of theembodiment of the sensor head 150 of FIG. 10.

As illustrated in FIGS. 10 and 11, the sensor head 150 includes a core162. The core 162 may be fabricated from any ferromagnetic material(e.g., iron, steel, nickel, cobalt). The core 162 has a cross axis yoke164 with a yoke portion 166. Four members 168, 170, 172, 174 of thecross axis yoke 164 extend radially outward in a plane from the yokeportion 166. The four members 168, 170, 172, 174 are substantiallyorthogonal to each other around the yoke portion 166. Each of the fourmembers 168, 170, 172, 174 may extend from the yoke portion 166 in anyconfiguration and for any length that enables each member to operate asdescribed herein. In some embodiments, the yoke 164 may have any numberof members that enables the yoke 164 to operate as described herein. Forexample, the sensor head 150 may have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ormore members that extend radially from the yoke portion 166. The one ormore members may be angularly spaced apart by approximately 10, 20, 30,40, 45, 60, 75, 90, 120, or 130 degrees, or any combination thereof.

As illustrated in FIG. 10, the driving pole 152 extends outward from theyoke portion 166 perpendicular to a planar surface defined by the yoke164. In addition, the four sensing poles 154, 156, 158, 160 extendoutward from the yoke 164 substantially perpendicular to the planarsurface defined by the yoke 164 and substantially parallel to drivingpole 152. The sensing pole 154 extends from the distal end of member168, the sensing pole 156 extends from the distal end of member 170, thesensing pole 158 extends from the distal end of member 172, and thesensing pole 160 extends from the distal end of member 174. In someembodiments, the core 162 may have any number of poles (includingdriving poles and sensing poles) extending from the yoke 164 thatenables the core 162 to operate as described herein. For example, thecore may have one driving pole and 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or moresensing poles extending from the yoke 164. Also, a driving coil 176 isdisposed about (e.g., wrapped around) the driving pole 152. Fourdetection coils 178, 180, 182, 184 are disposed about (e.g., wrappedaround) each of the respective sensing poles 154, 156, 158, 160.

In operation, an AC current is passed through the driving coil 176 toinduce the first magnetic flux portion 38. The first magnetic fluxportion 38 flows from the driving pole 152, through the target material14, to the four sensing poles 154, 156, 158, 160, where the respectivesensing coils 178, 180, 182, 184 detect the first magnetic flux portion38. As noted above, a change in the first magnetic flux portion 38 dueto a force applied to the target material 14 may be measured by thesensing coils 178, 180, 182, 184. In addition, the driving coil 176 mayalso emit leakage magnetic fluxes 40 that do not permeate the targetmaterial 14. The signal from the leakage magnetic fluxes 40 detected bythe sensing coils 178, 180, 182, 184 may constitute noise relative tothe measured signal from the first magnetic flux portion 38.

In accordance with the present disclosure, one or more magnetic shields11 (e.g., the magnetic shield 12, 62, 70, 92, 100, 130, 144) may bedisposed in the space between the driving pole 152 and each of therespective sensing poles 154, 156, 158, 160, or one magnetic shield(e.g., the magnetic shield 62, 70, 92, 100, 144) may be disposed about(e.g., wrapped around) the driving coil 176 of the driving pole 152, orany combination thereof. In some embodiments, more than one magneticshield (e.g., the magnetic shield 70, 92, 100, 130), coupled with eachother in any suitable manner (e.g., in series, in parallel, concentric,coaxial, telescopic, or any combination thereof), may be disposed in thespace 42 between the driving pole 152 and each of the respective sensingpoles 154, 156, 158, 160, or disposed about (e.g., wrapped around) thedriving coil 176 of the driving pole 152.

Technical effects of the subject matter disclosed herein include, butare not limited to, disposing one or more magnetic shields in themagnetostrictive sensing system to reduce or eliminate the leakage fluxbetween the driving pole and the sensing pole. Advantageously, theresulting magnetostrictive sensing system may have an increased dynamicsensing range. In addition, the magnetic shields may improve the signalto noise ratio of the magnetostrictive sensing system.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

The invention claimed is:
 1. A system comprising: a magnetostrictivesensor comprising: a driving coil configured to receive a first drivingcurrent and to emit a first magnetic flux portion through a target and asecond magnetic flux portion; a first sensing coil configured to receivethe first magnetic flux portion and to transmit a signal based at leastin part on the received first magnetic flux portion, wherein thereceived first magnetic flux portion is based at least in part on aforce on the target; and a magnetic shield disposed between the drivingcoil and the first sensing coil, wherein the magnetic shield isconfigured to reduce the second magnetic flux portion received by thefirst sensing coil, and the magnetic shield comprises a flexible circuitdisposed about the driving coil.
 2. The system of claim 1, comprising: adriving pole, wherein the driving coil is disposed about the drivingpole; and a first sensing pole, wherein the first sensing coil isdisposed about the first sensing pole.
 3. The system of claim 2, whereinthe magnetic shield is disposed about the driving pole.
 4. The system ofclaim 2, comprising a second sensing pole and a second sensing coildisposed about the second sensing pole, wherein the driving pole isdisposed between the first sensing pole and the second sensing pole. 5.The system of claim 1, wherein the magnetic shield comprises an innermagnetic shield disposed about the driving coil and an outer magneticshield disposed about the driving coil and the first sensing coil. 6.The system of claim 1, wherein the flexible circuit comprises acompensation coil configured to receive a second driving current and toemit a third magnetic flux portion with a magnitude substantially equalto the second magnetic flux portion and with a direction substantiallyopposite to the second magnetic flux portion.
 7. The system of claim 6,comprising a controller configured to control the second drivingcurrent.
 8. A system comprising: a magnetostrictive sensor comprising: adriving coil configured to receive a first driving current and to emit afirst magnetic flux portion through a target and a second magnetic fluxportion; a first sensing coil configured to receive the first magneticflux portion and to transmit a signal to a controller based at least inpart on the received first magnetic flux portion; and a magnetic shieldcomprising a flexible circuit, wherein the magnetic shield is disposedbetween the driving coil and the first sensing coil and the magneticshield is configured to reduce the second magnetic flux portion receivedby the first sensing coil; and the controller configured to determine aforce applied to the target based at least in part on the signal.
 9. Thesystem of claim 8, comprising: a driving pole, wherein the driving coilis disposed about the driving pole; and a first sensing pole, whereinthe first sensing coil is disposed about the first sensing pole.
 10. Thesystem of claim 9, wherein the magnetic shield is disposed about thedriving pole.
 11. The system of claim 8, wherein the magnetic shieldcomprises an inner magnetic shield disposed about the driving coil andan outer magnetic shield disposed about the driving coil and the firstsensing coil, wherein the outer magnetic shield is configured to reduceexternal electromagnetic interference received by the driving coil andthe first sensing coil.
 12. The system of claim 8, wherein the flexiblecircuit comprises a compensation coil and the controller is configuredto control a second driving current through the compensation coil toemit a third magnetic flux portion with a direction substantiallyopposite to the second magnetic flux portion.
 13. The system of claim12, wherein the controller is configured to control the second drivingcurrent based at least in part on a spacing between the driving coil andthe sensing coil, or a distance between the magnetostrictive sensor andthe target, or any combination thereof.
 14. The system of claim 8,wherein the controller is configured to determine the force applied tothe target of a turbine engine, a compressor, a pump, a generator, or acombustion engine, or any combination thereof.
 15. A method comprising:supplying a first current to a driving coil of a magnetostrictivesensor; emitting a first magnetic flux portion from the driving coilthrough a target; emitting a second magnetic flux portion from thedriving coil; sensing the first magnetic flux portion with a sensingcoil of the magnetostrictive sensor; and reducing the second magneticflux portion received by the sensing coil based at least in part on amagnetic shield of the magnetostrictive sensor disposed between thedriving coil and the sensing coil, wherein the magnetic shield comprisesa flexible circuit.
 16. The method of claim 15, comprising reducingnoise received by the sensing coil based at least in part on a housing,wherein the housing comprises a first layer configured to magneticshield the sensing coil from high frequency noise and a second layerconfigured to magnetic shield the sensing coil from low frequency noise.17. The method of claim 15, comprising: generating a signal based atleast in part on the first magnetic flux portion sensed with the sensingcoil; and determining a force on the target based at least in part onthe signal.
 18. The method of claim 15, comprising: supplying a secondcurrent to a compensation coil of the magnetic shield; and emitting athird magnetic flux portion from the compensation coil in a directionsubstantially opposite to the second magnetic flux portion.
 19. Themethod of claim 18, comprising controlling the second current to thecompensation coil based at least in part on a spacing between thedriving coil and the sensing coil, or a distance between themagnetostrictive sensor and the target, or any combination thereof.